Search

The optimal design methodologies in aeronautics are known to be constrained by the computational burden required by direct simulations. Due to this reason, the development of efficient metamodelling techniques represents nowadays an imperative need for the designers. In fact, surrogate models has been demonstrated to significantly reduce the number of high–fidelity evaluations, thus alleviating the computing effort. Over the last years, the aeronautical designers’ community has switched from a design approach predominantly based on direct simulations to an extensive use of metamodels. Recently, to further improve the efficiency, several dynamic approaches based on self–tuning parameters have been developed to support the metamodel construction. This work deals with the use of surrogate models based on Artificial Neural Network for the noise shielding of unconventional aircraft configurations. Here, the insertion loss field of a 2D airfoil is reproduced through advanced machine learning techniques. The relevant framework is the calculation of the noise emitted by innovative aircraft configurations by means of suitable corrections of existing well–assessed noise prediction tools. The self–tuning algorithm has demonstrated to be accurate and efficient, and the observed performance discloses the possibility to implement numerical strategies for the reliable and robust unconventional aircraft optimal design.&nbsp

In the frame of the European research project ARTEM (Aircraft noise Reduction Technologies and related Environmental iMpact), new aircraft architectures and alternative propulsion systems, e.g. Blended Wing Body (BWB) and geared turbofan engine concept, are investigated, as well as innovative noise reduction technologies such as metamaterials and low noise high-lift device systems. A noise impact assessment has been performed on a long-haul BWB concept developed by Roma Tre University, using the System Noise Prediction Tools of ONERA (CARMEN) and DLR (PANAM). First, shielding effects on the main noise sources are discussed, through installation effects hemi-spheres at chosen frequencies around the aircraft. Based on the shielding assessment, detailed take-off and landing procedures are simulated for several aircraft configurations. Two motorisations of the BWB are evaluated (BPR 8 and BPR 12), provided by RWTH Aachen. Finally, the most promising low noise technologies developed in the frame of ARTEM are applied, and their impact on noise levels on the ground is discussed. It can be demonstrated how the specific aircraft configuration, the engine type and the additional low-noise technology result in a significant overall noise reduction. A joint conference paper presents flyover auralisations based on these noise emission calculations.

This paper deals with the development of suitable surrogate models for the acoustic assessment of the shielding effects due to engine installation on top of unconventional aircraft configurations. The interest of the aeronautic community towards finding solutions to reduce the environmental impact has increased tremendously in the last decade, in particular to reduce acoustic emissions. The Advisory Council for Aviation Research and Innovation in Europe (ACARE) has in fact set ambitious noise reduction targets for 2050, which can only be reached through important technological advances such as the development of highly innovative configurations. Among solutions proposed in literature, one of the most promising and most investigated is the Blended Wing Body (BWB) aircraft configurations. Because of the peculiar center-body shape of this concept, the engines can be installed on top of the aircraft, making its noise shielding properties particular appealing. Therefore, the choice of the optimal position of the engines to maximize the masking effect represents a crucial aspect that must be taken into account from the early design stages. However, as experimental and historical data are not available in this context, there are no alternative to perform direct simulations for the acoustic assessment needed in conceptual design phase, which would lead to an unacceptable increase of computational resources for optimization purposes. A possible solution is to limit the number of performed simulation by using them to develop metamodels based on stochastic radial basic functions for the evaluation of the acoustic shielding factor, instead of calculating the actual value at each call of the objective functions. Specifically, starting from few high–fidelity simulations by means of a bidimensional integral solver based on the convective Helmholtz equation, an adaptive metamodel is developed for the evaluation of the shielding factor of airfoils, which takes into account the variation of crucial design variables.

One of the topics of research in ANIMA is the effectiveness of the use of a Virtual reality device for credible communication and engagement with people around airports. As input to this kind of device one needs realistic noise signatures. For existing aircraft, experimental data (aircraft noise recordings) can be used. For novel aircraft however, only existing on the drawing board, such experimental data is obviously not available. To fill this gap, noise predictions will be made with the Noise Reduction Solutions Simulator, which is part of the Virtual Community Toolchain that is being developed in ANIMA WP4. This Simulator will be capable of predicting noise spectra of novel aircraft including noise reduction technology concepts, which, in turn, can be fed to noise synthesis tools (in this report also called auralization tools) to create realistic noise signatures. This combination of noise prediction and noise synthesis will be called auralization toolchain in the following. At present the Noise Reduction Solutions Simulator is still under development and no reliable noise predictions can yet be made. However, an important aspect of the auralization toolchain can already be tested: the interface between the Simulator and noise synthesis tools. The goal is to have a noise prediction tool that can be plugged to any available noise synthesis tool. This report describes the methodology used in the Simulator, comprised of two tools, FRIDA and SOPRANO, to get noise spectra from data characterizing an aircraft flight. Additionally, a representative sample datafile is described, with which this interface test can be performed, and which will allow for an early detection of any issues interfacing the components.

Air trac growth and the expansion of urban areas around airports make the aviation community noise a key aspect of aircraft design. The analysis of innovative con gu- rations is becoming activity of primary interest within the scienti c community. The current e ort to attain the strict noise{abatement targets imposed by the authorities risks to be pro tless without a signi cant technological breakthrough. A promising innovative con guration in terms of noise reduction is the Blended{Wing{Body air- craft. Indeed, the installation of the propulsion system above the centre{body surface ensures a signi cant masking e ect of the engine noise components. The lack of ex- perimental data needed to validate the advantages introduced by these technologies, and therefore carry out parametric analysis, can only be overcome by formulating reliable and cost{e ective models to predict the noise shielding induced by engines installation on unconventional geometries. The present work introduces the develop- ment of tailored models for the correction of the existing semi-empirical prediction techniques. Such models are embedded within the modules of the existing conceptual design framework FRIDA. Without excluding other disciplines, the introduction of a noise prediction tool allows to cast a wide net in the research of optimal con guration in the future aviation context.

Air trac growth and the expansion of urban areas around airports make the aviation community noise a key aspect of aircraft design. The analysis of innovative con gu- rations is becoming activity of primary interest within the scienti c community. The current e ort to attain the strict noise{abatement targets imposed by the authorities risks to be pro tless without a signi cant technological breakthrough. A promising innovative con guration in terms of noise reduction is the Blended{Wing{Body air- craft. Indeed, the installation of the propulsion system above the centre{body surface ensures a signi cant masking e ect of the engine noise components. The lack of ex- perimental data needed to validate the advantages introduced by these technologies, and therefore carry out parametric analysis, can only be overcome by formulating reliable and cost{e ective models to predict the noise shielding induced by engines installation on unconventional geometries. The present work introduces the develop- ment of tailored models for the correction of the existing semi-empirical prediction techniques. Such models are embedded within the modules of the existing conceptual design framework FRIDA. Without excluding other disciplines, the introduction of a noise prediction tool allows to cast a wide net in the research of optimal con guration in the future aviation context.

The present work reports an investigation on the use of adaptive metamodels based on radial basis functions (RBFs) for aeroacoustic applications of highly innovative configurations. The relevance of the topic lies on the paramount importance of metamodelling techniques within the design optimisation process of disruptive aircraft layouts. Indeed, the air traffic growth, consequently the hard environmental constraints imposed by regulations, will make a technological breakthrough, an imperative need within few years. As a consequence, the engineering community is paying particular attention to the development of innovative techniques for the design of unconventional configurations. For this class of applications, the designer cannot successfully rely on historical data or low-fidelity models, and the expensive direct simulations remain the only valuable design strategy. In this regard, it can be demonstrated that the use of surrogate models, i.e., metamodels, significantly reduces the computing costs, especially in view of a robust approach to the optimised design. In order to further improve the efficiency of metamodel-based techniques, dynamic approaches based on hyperparameter optimisation and adaptive sampling procedures have been recently developed. The case study presented here pertains the exploiting of dynamic RBF-based metamodels for noise shielding applications. The analysis of the metamodel performances and its convergence properties shows how the final number of direct simulations is significantly reduced by the hyperparameter optimisation algorithm, still strongly depending on the choice of the RBF kernel function.

The paper deals with a community-oriented approach to the multiobjective optimisation of sustainable takeoff and landing procedures of commercial aircraft. The objective functions to be minimised are defined as the measure of area surrounding the airport where the Sound Exposure Level (SEL) is higher than 60 dBA, and the amount of fuel burned during the procedure. The first merit factor is a measure of the number of citizens affected by a potentially harmful noise level, whereas the second is proportional to the chemical emissions. The novelty of the present approach is the use of a criterion based on sound quality for the selection of the optimal procedure from the Pareto front set. The spectrum of the noise produced by each non-dominated solution is compared to a reference spectrum, the target sound. This is synthesised to meet the acceptance requirements that emerged by a campaign of psychometric tests. The rationale underlying the research is tightly linked to the expected transformation of civil aviation, with the advent of new air transport solutions in urban and suburban environments. The breakthrough nature of the emerging scenarios requires a drastic renewal of the approaches used in the management of operations, and the present work represents a contribution to this evolution. The optimisation is attained adopting a global, deterministic method, and numerical results are obtained for single- and twin-aisle aircraft.

The present work deals with the development of an innovative approach to the weight estimation in the conceptual design of a Hybrid-Electric-Powered (HEP) Blended Wing Body (BWB) commercial aircraft. In the last few decades, the improvement of the environmental impact of civil aviation has been the major concern of the aeronautical engineering community, in order to guarantee the sustainable development of the system in presence of a constantly growing market demand. The sustained effort in the improvement of the overall efficiency of conventional aircraft has produced a new generation of vehicles with an extremely low level of emissions and noise, capable of covering the community requirements in the short term. Unfortunately, the remarkable improvements achieved represent the asymptotic limit reachable through the incremental enhancement of existing concepts. Any further improvement to conform to the strict future environmental target will be possible only through the introduction of breakthrough concepts. The aeronautical engineering community is thus concentrating the research on unconventional airframes, innovative low-noise technologies, and alternative propulsion systems. The BWB is one of the most promising layouts in terms of noise emissions and chemical pollution. The further reduction of fuel consumption that can be achieved with gas/electric hybridisation of the power-plant is herein addressed in the context of multidisciplinary analyses. In particular, the payload and range limits are assessed in relation to the technological development of the electric components of the propulsion system. The present work explores the potentialities of an energy-based approach for the initial sizing of a HEP unconventional aircraft in the early conceptual phase of the design. A detailed parametric analysis has been carried out to emphasise how payload, range, and degree of hybridisation are strictly connected in terms of feasible mission requirements and related to the reasonable expectations of development of electric components suitable for aeronautical applications.

The current work deals with multi-objective optimisations including financial merit factors in the multi- disciplinary conceptual design of a commercial aircraft with a specific focus on noise social cost. The results of optimisations using financial and performance-oriented objective functions have been analysed and combined in a multi-objective optimisation problem using a three-dimensional objective vector. The main novelty of the present work is the analysis of social cost noise fees effectiveness integrated in financial models embracing a wider group of stakeholders’ interests. The foundations of this research lie on the air traffic increase envisaged in the next decades and the contextual growth of the urban areas nearby airport facilities. This scenario requires the aeronautical industry to handle the environment challenge taking into account all the social and economic effects. Indeed, the consolidated technology has approached a saturation point, therefore breakthrough concepts and configurations are mandatory. This matter is addressed as a highly multi-disciplinary problem within conceptual design framework. The financial model proposed is shown to highlight the need of appropriate noise fees as instruments to push all stakeholders towards a technology radical renewal and encourage the aeronautical industry towards a shared strategy in the development of an eco-friendly commercial aviation system.

The airframe noise of a 1:2 scaled aircraft model is investigated through a series of experiments in the hard walled closed test section of a large non-anechoic wind tunnel. A surface mounted phased microphone array is used to acquire the wall pressure fluctuations generated by the interaction of the wind tunnel flow and the propagating noise. Data from two measurement campaigns are analysed. The wind tunnel acoustic behaviour and the array performance are first assessed evaluating the results obtained from a reference sound source installed in the centre of the test section. The combination of different airflow speeds, array positions and sound sources are tested. The airframe noise is evaluated acquiring pressure fluctuations in different configurations. The main parameters varied during the tests are the flight configuration, the speed of the airflow, the incidence angle of the model and the position of the microphone array. Data are processed and then analysed in the frequency domain and using a conventional beamforming algorithm to retrieve the sound source maps over the regions of interest. Source maps are deconvolved with a CLEAN-SC routine and single source contributions determined through integration of auto-powers. The resulting spectra are finally scaled determining the exponents of the pertinent scaling laws.

The aeroacoustics of an innovative regional turboprop aircraft is experimentally investigated on a 6.5 scaled model. The measurement campaign was performed at the RUAG Large Subsonic Wind Tunnel in Emmen. The model was mounted on a ceiling strut in the 7-by-5 meters test section, not acoustically treated. The aeroacoustic noise generated by the aircraft model was evaluated analyzing the pressure fluctuations acquired through a phased array of 144 microphones installed on a flat-plate on the test section floor. Pressure fluctuations were acquired in different configurations the most important ones being: the baseline solution (no innovative device applied) with engine on and the model equipped with lined Flap. For the engine on configuration, take-off and approach settings were tested, whereas only the landing configurations was investigated for the baseline lined flap comparison. The main parameters varied during the tests were: the propeller thrust, the propeller revolutions per minute, the speed of the air-flow, the incidence angle of the aircraft and the position of the microphone array. Data were processed and then analyzed in the frequency domain and using a conventional beamforming algorithm to retrieve the sound source map over the areas of interest. Source maps were deconvolved with a CLEAN-SC routine and single source contributions determined through integration of auto-powers.

The paper deals with the use of sound quality as a criterion for the ranking of the non-dominated solutions of a multi-objective design optimization of aircraft oriented to environmental sustainability. The solutions belonging to the approximated Pareto front of the bi-objective minimization of the fuel burned and the noise level at certification points are ranked with respect to the matching of the emitted noise spectrum against a reference target sound. The latter is a synthesized aircraft sound satisfying sound-quality specifications coming from psychometric tests conducted in the EC-funded projects (Sound Engineering for Aircraft) and COSMA (Community Oriented Solutions to Minimize aircraft noise Annoyance). Indeed, the environmental impact of civil aviation is nowadays the most urgent concerns in the development a sustainable air transportation system since, during the last three decades, the air traffic growth has generated a remarkable increase of the operative airports. In parallel, the urban development has led to the inclusion of secondary airports within the city areas. As a consequence, the number of people directly exposed to aircraft noise has sensibly increased. In such a social context, the designers can hardly attain further substantial technical improvements as the standard concepts and technologies have reached a development saturation, thus imposing the identification of breakthrough technologies and innovative concepts, with a plausible date of entry into service not early than 2050. The research initiated in SEFA and further developed in its follow-up COSMA aims at the alleviation of the noise impact on the population, switching the attention on noise quality rather than noise level, in order to provide to designers additional tools to mitigate the effects of noise. The present work is the evolution within a multi-objective context of the early attempts of sound-quality-oriented MDO developed during those projects.

The present work deals with a multi-objective optimisation approach to incorporate up-to-date financial models in the multidisciplinary conceptual design of a commercial aircraft. Design optimisations based on financial objective functions are compared to standard performance-based optimal solutions. The main novelty is in the extension of the financial models to the long-term investments of a wider group of stakeholders. The rationale underlying this research stems from two considerations: (i) the environmentally sustainable development of the air transportation system in the next 20 years is subordinate to breakthrough technologies, since the consolidated ones have reached their saturation point; (ii) the economic impacts of highly innovative concepts on the stakeholders chain is still uncertain. The problem is addressed at the conceptual design level and the analysis is performed within a comprehensive multidisciplinary framework, adopting all the technical constraints required in aeronautical design. The Pareto fronts obtained using performance and financial merit factors, reveal that the proposed financial model yields highly efficient, technically sound concepts. The design space point corresponding to the negative cash flows minimum turned out to be very close to the one corresponding to minimum acoustic emissions, confirming that the financial model drives the optimiser towards environment-friendly designs.

This paper reports the results of the aeroacoustics study of an Unmanned Aerial Vehicle (UAV) experimentally investigated on a scaled prototype model. The measurement campaign were performed at the RUAG Large Subsonic Wind Tunnel in Emmen. The model was mounted on a ceiling strut in the 7-by-5 meters test section. The aeroacoustic noise generated by the UAV was evaluated analysing the pressure fluctuations acquired through a phased array of 144 microphones installed on a flat-plate on the ground of the test section floor. Pressure fluctuations were acquired in different configurations. The main parameters varied during the tests were: the velocity of the air-flow, the incidence angle of the UAV and the presence of the landing gears. Flaps were always deployed. The directivity source contribution to the overall noise at various emission angles is determined as well, for each configuration, moving the array along the flow direction. Data were processed and then analysed in the frequency domain and using a conventional beamforming algorithm to retrieve the sound source map over the areas of interest. Source maps were deconvolved with a CLEAN-SC routine and single source contributions determined through integration of auto-powers. The resulting spectra were finally scaled to flight conditions.

Aircraft noise is nowadays one of the most urgent concerns in the development of the air transportation system. The tremendous grow rate of the number of passengers during the last two decades has generated a significant increase of the number of airports, with a commercial rebirth of secondary air terminal. As a consequence, the number of people affected every day by the noise produced by aircraft operations has sensibly increased. Within this framework, the effort of the research community during the last 20 years has concentrated, according to the regulation, on the abatement of the noise level. Lately, the possibility to include in this process considerations related to the annoyance produced by the exposition to aviation noise has received a major improvement. Such an approach would allow the designer to explore unconventional possibilities, widening the horizon of the future technological scenarios and multiplying the options available to reduce the impact of the community noise on the population. One of the major difficulties in the integration of perception-based considerations resides in the not easy translation of psychoacoustic indicators in terms of design variables. The present papers describes the approaches developed during the EU-funded research projects SEFA (Sound Engineering for Aircraft, FP6/2004-2007) and its follow-up COSMA (Community Oriented Solutions to Minimize aircraft noise Annoyance, FP7/2009 on). The problem is here approached from the point of view of a research engineer in aeronautical sciences. Specifically, the mechanism identified to drive the optimization process to weakly annoying configuration is described. Special attention is payed to the description of the relevance of annoyance related objectives in the resulting workflow, and how these objectives are capable to drive the designers' choices.

The environment challenge and the expected growth of the market demand impose a technology breakthrough within the aeronautical industry. Although several innovative configurations of airplanes have been analyzed, none of them has been yet chosen as the most promising candidate. One of the reasons is related to the not yet known economic impacts of these architectures, since the life-cycle costs and infrastructural investments analysis are still unclear and therefore the current modules cannot be reliably directly applied. Such cost categories, in the last decades, have been mainly related to design and operational factors, as aircraft fuel-weight and empty-weight, with only an indirect link to the aircraft performance, particularly from the environmental viewpoint. This work presents a novel approach to include up-to-date models of life-cycle costs for low-noise aircraft from an airliner perspective. The situation is here addressed as a multidisciplinary conceptual design problem including the above up-to-date models. The possibility to estimate at the conceptual design stage the economic and financial implications of a radically new concept would substantially increase the possibility for the manufacturers to rank and select the most promising ideas.